Attack Of The Dreaded Fruit Flies

What IS IT with fruit flies?? I can't think of anything smaller in this world that is MORE annoying. They are impossible to kill with a quick swat. And there is usually some mystery behind their presence, as I can never locate the reason why they suddenly take up house in my house.

So, as you may have guessed, we have been batting at the air for two weeks now. They are not only in the kitchen, but finding their way into the bathrooms and other rooms now too. I've been trying my best to keep food and fruit absent from the open. What is the deal?

I have a very strong stomach, but it wants to turn when I recall having to take care and breed fruit flies for weeks during college for my Genetics class. (I never have been able to erase from my mind that yeasty smell of the goo I had to give them for food).

What do they want from me?????